Fragile X is caused by a single gene disorder, carried by about one in 260 women and one in 800 men. It affects about one in 3600 males and one in 4000-6000 females. There is no cure.

For journalist Kate Spicer, making the film was a way of portraying Tom as a man, not a label.

“If I'm honest, we made the journey into a film because if we hadn't, we could not have afforded the time to do it justice. We never wanted it to be about shuffling Tom along for what they call a 'grip and grin',” she says from her London home.

But, as the film documents, convincing Tom to go on the grand adventure in the first place, then chasing Metallica across Nevada and California in a campervan, was not an easy ride.

“I felt completely torn between caring for Tom and trying to be a solid, stable presence for him and driving the action in the film forward and making things happen,” says Spicer.

The charm of the film lies in that journey – although the destination ends up being pretty great too.

The screening of Mission to Lars has been welcomed by the Fragile X Association of Australia, which supports families here living with condition.

“Every week in Australia one child is born who is fully affected by Fragile X and 20 children are born who are carriers,” says FXAA project officer Joan MacDonald.

“This film is a fabulous awareness vehicle for Fragile X. Awareness is so important because Fragile X is a genetic condition. People might have three children before they even realise that they have it. Sufferers can also be misdiagnosed with Autism, Aspergers or other conditions.”

Spicer says she's grateful for the support the FXAA has thrown behind the film, saying they have a mutual interest in getting it distributed.

“For them it's raising awareness of the single biggest cause of inherited learning disability and for us it's all about taking our brother and Lars' story to as many people as possible.”

With the theme of Mission to Lars all about the ties that bind us as families, it's interesting to learn that the tensions making it caused between Spicer and her filmmaker brother Will have not been fully resolved.

On the flipside, it has brought Spicer closer to Tom.

“It moves me almost to tears how much the trip has changed him and how the world sees him and how we relate to each other. It's brilliant.”

Mission to Lars screens as part of the Brisbane International Film Festival this Saturday 17 November at 2.30pm at Palace Petrie Barracks 5. More information at www.biff.com.au

If you see Mission to Lars, tweet your review using the hashtag #biffreviews, for your chance to win tickets to the closing night screening of Anna Karenina.